In a known manner, rotary electrical machines comprise a stator and a rotor which is integral with a shaft. The rotor can be integral with a driving and/or driven shaft, and can belong to a rotary electrical machine in the form of an alternator, as described in document EP0803962, or an electrical machine as described in document EP0831580. The electrical machine comprises a housing which supports the stator. This housing is configured to rotate the rotor shaft, for example by means of bearings.
The rotor comprises a body formed by a stack of metal sheets maintained in the form of a set by means of an appropriate securing system, such as rivets which pass through the rotor axially from one side to the other. The rotor comprises poles which are formed for example by permanent magnets accommodated in cavities provided in the magnetic mass of the rotor, as described for example in document EP0803962. Alternatively, in a so-called “projecting” poles architecture, the poles are formed by coils wound around arms of the rotor.
The stator comprises a ferromagnetic body constituted by a stack of thin plates, as well as a winding received in notches in the stator which are open towards the interior. The winding is formed by a plurality of phase windings each corresponding to a phase of the machine. Each winding is formed by a series of turns each formed by one or a plurality of continuous wires which are generally made of copper. These wires follow an undulating form, and have loop structures situated alternately on each side of the stator, connecting to one another segment structures situated inside notches. A series of loop structures extending from one side of the stator constitutes a chignon of the winding.
The winding of the stator is conventionally produced phase by phase. For example, for a hexaphase machine, the six phase windings are produced in the same manner one after the other. Closure wedges are inserted in the notches during the production of each phase winding.
The disadvantage of this type of winding is that the chignons of the first phase winding impede the insertion of the winding of the following phase, and so on, the final phase being obstructed by the chignons of all the preceding phase windings.
In order to solve this problem, an intermediate forming operation is carried out, consisting of clearing the space above and below the notches of the following phase to be inserted, by application in the chignons of a radial force going from the interior towards the exterior of the stator. This force is applied by means of clamping jaws which act simultaneously and identically on all the lower and upper parts of the chignons of the winding.
However, the force which is transmitted by the clamping jaws on the wires of the chignons induces a force in the notches which tends to eject the notch closure wedges, or the wires, in the case when the method does not involve the use of closure wedges. The radial expansion of the clamping jaws is thus limited by this phenomenon, which therefore does not make it possible to clear enough space in the notches of the stator for the purpose of inserting the following phase windings.
The consequence is that the notches are not filled in an optimum manner, such that the coefficient of filling of the notches (i.e. the ratio between the cross-section of the bare conductive wire, and the complete cross-section of the notch), and thus the performance of the machine, are downgraded. In fact, the known methods make it possible to produce wound stators with a maximum filling level of 52% for three-phase applications and 50% for hexaphase applications.